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basic drug?

acid drug?

pH

pKa

ionized (%)

Example

1) The pH of the stomach is 2.5. The pKa of sodium pentothal is
7.4 and it is acidic. If a patient is given sodium pentothal orally
instead of IV, will it put the patient to sleep? See the example below:

None of the sodium pentothal is ionized in the stomach.
Therefore the patient would absorb 100% of this medication and it would put him
to sleep.

2) A basic drug with a pKa of 7.8 is a known teratogen.
If given IV to a pregnant woman whose blood pH is 7.4, will this drug cross the
placenta and effect the baby? See the example below:

In this example, 72% of the drug is ionized which means 28% of the drug
is unionized and will pass through the placenta to effect the baby.

If pKa - pH > 1 then the solution is 99-100%
ionized or 99-100% unionized*

Slight discrepancy
between this statement and formula used for calculator. Formula used
indicates solutions would be 90-100% ionized or unionized. These
rules were taken from my Nursing 605 course. My chemistry background
is weak and I'm unable to verify the formula used. Other than this,
the formula follows the basic rules.